DESCRIPTION: This proposal will explore the nature of the human intestinal microbiome in healthy children and children with gastrointestinal (GI) disorders. The overall goal is to obtain a robust knowledge-base of the intestinal microbiome in a set of GI disorders that represent a broad spectrum of important disease phenotypes in pediatric gastroenterology. In addition to the detailed clinical assessment of healthy children and children with irritable bowel syndrome, constipation, and inflammatory bowel disease (Crohn disease), multiple strategies will be deployed to navigate and understand the nature of the intestinal microbiome in childhood. These strategies will include Sanger sequencing and pyrosequencing-based strategies to understand the detailed composition of microbes in healthy and disease groups. Whole genome shotgun sequencing will be used as an exploratory strategy to explore metagenomes in patients in a comprehensive manner. Microarray-based hybridization with the PhyloChip, denaturing HPLC, quantitative real-time PCR, and bacterial fluorescence in situ hybridization probes will be applied as complementary strategies to gain an understanding of the intestinal microbiome from various perspectives in molecular microbiology. The first hypothesis is that healthy children have a core, identifiable microbiome. The second hypothesis is that disease-specific signatures in the human microbiome are present, and these microbial signatures may be correlated with pediatric gastrointestinal disease phenotypes. This proposal will explore the nature of core and variable human microbiomes in pre-adolescent healthy children and children with GI disorders. Finally, spatial architecture of intestinal microbes and human factors will be studied in order to examine higher-order alterations in microbial communities in different disease states and the relative contributions of human immune response genes. PUBLIC HEALTH RELEVANCE: This project will increase our understanding of the microbes that reside in the intestines of healthy children and children with various intestinal disorders. The findings from this project will enable scientists to determine the nature of beneficial microbial populations in intestines of healthy children, and whether specific differences in groups of microbes may contribute to diseases in children. Ultimately, the discoveries from this project may allow physicians to manipulate microbes in the intestine in order to promote health and cure or prevent disease.